More than 40,000 signed a petition backing the Let Our Kids Be Kids campaignPeter Macdiarmid/Getty Images

Thousands of children are expected to miss school on 3 May as part of a nationwide "strike" over excessive exams. Parents are pulling their children out of school as they call for an end to the "shambolic" standard assessment tests (SATs), which they say stifles creativity.

More than 40,000 people have signed a petition supporting the Let Our Kids Be Kids campaign. The group, started by Year 2 parents, calls for parents to give their children the day off school and have "educational fun instead".

The petition said: "We want our kids to be kids again and enjoy learning for learning's sake not for Ofsted results or league table figures. In May, children in Year 2 sit a whole week's worth of exams. These children are 6 or 7 years old!

"All year their curriculum has been centred around comprehension and arithmetic in order to pass these tests. Outdoor learning has decreased, childhood anxiety has increased, games have been replaced with grammar, playing with punctuation."

The protest originally concerned Key Stage 1 testing for seven-year-olds but later expanded its scope to include SATs tests taken by 11-year-olds. Both have been made harder in an attempt by the government to drive up standards.

The number of those taking part is uncertain but participants have been taking to social media to post pictures of the "kids strike". One event in Brighton showed at least 100 parents and children in a park listening to speakers.

Education Secretary Nicky Morgan condemned the strike, warning it would damage children's learning. Speaking at the National Association of Head Teachers' annual conference on the weekend, she said: "Keeping children home, even for a day, is harmful to their education and I think it undermines how hard you as heads are working."

She added "more rigorous" tests would help address the gap in literacy standards between England and Korea, Singapore and Ireland.

Lucy Powell, the shadow education secretary, said she did not condone the strike but accused the government of creating "chaos". Labour said the Department for Education (DfE) had published, updated or clarified on average at least one primary assessment document or resource every other working day since September.

Powell said: "This government is creating chaos and confusion in primary assessment in schools, with a huge number of changes to SATs specifications since children started school last September. Ongoing assessment is really important to help teachers and parents support their children's education and to close any gaps in knowledge so all children can do well at school.

"However, the way this government has handled the assessment regime means that parents and teachers are lacking confidence in school tests and the assessment system is being undermined."